Chemical mechanical polishing using fluorescence-based endpoint detection

ABSTRACT

A polishing tool and methodology are disclosed, particularly useful for chemical mechanical polish (CMP) applications (e.g., polishing and planarizing). In an embodiment, the tool includes a carrier structure configured to support a workpiece, a polishing pad configured to rotate and polish at least a portion of the workpiece, a source configured to generate excitation radiation directed towards the workpiece, and a detector configured to receive fluorescence radiation from the workpiece. The fluorescence radiation is generated by absorption of the excitation radiation by a polymer material on the workpiece. The polishing tool also includes a controller configured to, based on a magnitude of the received fluorescence radiation, change at least one operating condition of the polishing tool. For instance, the controller can speed or slow the polishing process, and stop the polishing process when a target thickness is achieved.

BACKGROUND

Chemical mechanical polishing (CMP) is a process of smoothing surfaces with the combination of chemical and mechanical forces. In conjunction with a polishing pad, a chemically reactive slurry containing an abrasive is used to polish or planarize the surface of semiconductor wafers, metals, nanofiber materials, and other substrates. When used for semiconductor wafers, the polishing pad and wafer are pressed together by a polishing head and the wafer is held in place by a plastic retaining ring. The polishing head rotates about an axis of rotation that is different from the axis of rotation for the wafer. The CMP process can be used to remove wafer material and reduce irregular topography to provide a flat or planar wafer. Accordingly, CMP is useful to prepare a wafer for lithography and formation of circuits. Recently, CMP has been used for polishing surfaces of polymeric films. There are a number of non-trivial issues associated with achieving acceptable polishing results when dealing with polymeric materials.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example CMP system.

FIG. 2 illustrates a portion of an example CMP system with integrated fluorescence detection, in accordance with an embodiment of the present disclosure.

FIG. 3 is a graph of measured fluorescence for various polymer thicknesses, in accordance with some embodiments of the present disclosure.

FIGS. 4A-4C illustrate cross-sections of a bridge interposer fabricated using a CMP process, in accordance with some embodiments of the present disclosure.

FIGS. 5A-5C illustrate cross-sections of another bridge interposer fabricated using a CMP process, in accordance with some embodiments of the present disclosure.

FIG. 6 illustrates a fluorescence-integrated CMP process on a panel that includes multiple bridge interposers, in accordance with an embodiment of the present disclosure.

FIG. 7 is a flow chart of an example method for controlling a CMP process using fluorescence-based measurements, in accordance with an embodiment of the present disclosure.

FIG. 8 illustrates an example computer system that can be used to control a CMP process, in accordance with some embodiments of the present disclosure.

The Figures depict various embodiments of the present disclosure for purposes of illustration only. Numerous variations, configurations, and other embodiments will be apparent from the following detailed discussion.

DETAILED DESCRIPTION

Techniques are disclosed for polishing a polymer material. The techniques are particularly well-suited to chemical mechanical polishing (CMP) applications, but other uses will be appreciated in light of the disclosure. In any such cases, the techniques include the use of fluorescence-based measurements to provide real-time thickness observations of a polymer material as it is being polished. In an embodiment, a CMP tool is programmed or otherwise configured to bring the polymer material, via a carrier structure, into contact with a polishing pad, and to rotate the polishing pad to polish the polymer material. The tool is further configured to direct excitation radiation towards the polymer material, and receive fluorescence radiation from the polymer material. The fluorescence radiation is generated from absorption of the excitation radiation. The tool is further configured to adjust an operating condition of at least one of the polishing pad and the carrier structure based on a magnitude of the received fluorescence radiation. For instance, the CMP tool may halt rotation of the polishing pad, increase a rotation speed of the polishing pad, decrease the rotation speed of the polishing pad, or actuate the carrier structure to move the polymer material away from the polishing pad, or some combination of these. Numerous variations will be appreciated.

General Overview

As noted above, there are a number of non-trivial issues associated with achieving acceptable polishing results when dealing with polymeric materials. For example, existing panel-level polymer dielectric CMP equipment use time-based recipes to determine process endpoint. Such time-based approaches fail to guarantee a suitable uniform polymer dielectric thickness output between panels, particularly over time. Although there may be any number of contributors to this non-uniformity, some include variation in polymer dielectric thickness incoming to the CMP process, as well as pad-life induced process shifts in the CMP process. So, for instance, panels with lower incoming polymer dielectric thicknesses yield lower polymer dielectric thicknesses post CMP. Accordingly, it is difficult to control the final thickness of a polymer film when using CMP.

Thus, and according to an embodiment of the present disclosure, a CMP system and operating method are provided herein that integrate fluorescence spectroscopic techniques to detect real-time thickness changes and provide reliable endpoint thickness control. Many polymers, such as ones used in semiconductor fabrication and packaging, exhibit fluorescent properties in certain wavelength regions. Accordingly, and as will be appreciated in light of this disclosure, the measured fluorescence from these polymer materials can be used to determine, or at least estimate, a thickness of the polymer material. In one embodiment, a substrate polishing tool includes a carrier structure configured to support a workpiece, a polishing pad configured to rotate and polish at least a portion of the workpiece, a source configured to generate excitation radiation directed towards the workpiece, and a detector configured to receive fluorescence radiation from the workpiece. The fluorescence radiation is generated by absorption of the excitation radiation by a polymer material on the workpiece. The substrate polishing tool also includes a controller configured to, based on a magnitude of the received fluorescence radiation, change at least one operating condition of the substrate polishing tool. One such example operating condition includes ceasing the polishing of the workpiece once a desired thickness of a polymer material on the workpiece has been achieved. Numerous configurations and variations will be apparent in light of this disclosure.

While generally referred to herein as “chemical mechanical polishing” or “CMP” for consistency and ease of understanding the present disclosure, the disclosed methods are not limited to that specific terminology and alternately can be referred to, for example, as polishing, planarization, leveling, smoothing, recessing, or other similar terms.

Polishing Tool

Referring to FIG. 1, a substrate polishing tool 100 is presented that includes a platen 102 and carrier structure 106. A polishing pad 104 is supported on platen 102 while a workpiece 108 to be polished is coupled to an underside of carrier structure 106. Workpiece 108 may be, for example, a semiconductor wafer, a die, or a panel of connected structures, to name a few examples. Workpiece 108 may be adhered to carrier structure 106 by frictional forces, an adhesive, magnetics, vacuum, or other suitable means. Carrier structure 106 may apply a downward force on workpiece 108 during polishing. During a polishing stage, workpiece 108 is rotated by carrier structure 106 about first axis 107 and in contact with polishing pad 104 wet with slurry 112. Polishing pad 104 and platen 102 rotate about a second axis 109. The rotation of workpiece 108 and polishing pad 104 may be in the same direction or in opposite directions. A slurry feed 112 may be used to dispense slurry 110 onto polishing pad 104, as needed, during polishing.

Polishing of traditional semiconductor materials such as silicon, silicon oxide, or silicon nitride typically use friction-based sensors or reflectance measurements to determine a remaining thickness of the material as it is being polished. Although CMP of common crystalline semiconductor materials has been well established, CMP of polymer materials involves additional non-trivial challenges. Polymer dielectric films have become widely used in various semiconductor devices, microelectromechanical systems (MEMS), and packaging structures. In many applications, such films need to be planarized like any other dielectric material when performing a layer-by-layer fabrication process. Controlling the final thickness of the polymer films can be critical for certain applications. For example, films that are not polished enough (e.g., too thick) may provide too much insulating material that breaks the electrical connection between conductive layers, while films that are polished too much (e.g., too thin) may cause damage to underlying structures within or beneath the polymer film.

One application of polymer films in the semiconductor industry is as a fill dielectric material in bridge interposer structures. The bridge interposer structure provides an interconnect packaging substrate for multiple die to be packaged together on the same substrate. Polymer materials are used as the dielectric around the various conductive pathways and vias of each metal layer in the interconnect structure. Examples of such bridge interposer structures are provided in FIGS. 3 and 4 and will be discussed in turn.

As further noted above, while traditional CMP processes can be performed to polish and planarize such polymer dielectric materials, there is little control of the final thickness beyond a trial and error process. To this end, tool 100 can be modified according to an embodiment of the present disclosure, such that the tool will be configured to execute a thickness determination of polymer films during the polishing process by using fluorescence measurements of the polymer film. Polymer-based dielectrics, such as, for example, Ajinomoto build-up film (ABF), exhibit ultraviolet (UV) fluorescence for excitation wavelengths between about 340 nm and 360 nm. Accordingly, a UV source can provide excitation radiation towards a polymer film while a detector receives the fluorescence radiation (e.g., around 395 nm for ABF). The magnitude of the received fluorescence can be used to determine a current thickness of the polymer film.

According to one such embodiment, a controller (such as the controller of the CMP tool, or a dedicated controller that interfaces with the CMP tool) is programmed or otherwise designed to control operations of the CMP tool by using the fluorescence measurements to affect one or more operating conditions of the CMP tool. For example, the fluorescence measurements may be used to continually monitor the thickness of a polymer film of a workpiece. When the thickness reaches a particular threshold (e.g., a desired final thickness), the controller may halt the rotation of the polishing pad to cease further polishing of the polymer film and may further remove the workpiece from the polishing pad, according to some such embodiments.

Integrated Fluorescence Endpoint Detection

FIG. 2 illustrates a portion of a substrate polishing tool 200 that includes polishing pad 104, carrier structure 106, and workpiece 108 as described above with reference to FIG. 1. In addition, and according to an embodiment of the present disclosure, substrate polishing tool 200 includes a window 202 through a portion of polishing pad 104 to provide optical access to workpiece 108 as it is being polished by polishing pad 104. Window 202 may extend through an entire thickness of polishing pad 104. In other examples, window 202 extends through a portion of the thickness of polishing pad 104 and an optically transparent cap 204 is provided to prevent any particles or slurry from falling through window 202.

According to an embodiment, window 202 is provided through polishing pad 104 in order to allow fluorescence measurements to be taken from one or more polymer films present on workpiece 108. To this end, a first optical fiber 206 can deliver excitation radiation 210 via window 202 and directed towards workpiece 108. Excitation radiation may be absorbed by the one or more polymer films on workpiece 108, which generates fluorescence radiation 212 collected by a second optical fiber 208. Either or both first optical fiber 206 and second optical fiber 208 can represent a single fiber or a bundle of optical fibers. In some embodiments, first optical fiber 206 and second optical fiber 208 are angled from one another in some fashion to reduce the amount of excitation radiation 210 received by second optical fiber 208. In other embodiments, communication mediums other than optical fibers can be used, such as waveguide structures or other radiation transport mediums. Alternatively, some embodiments don't include optical fibers or any other communication medium, and instead place the source 214 and optical detector 216 (to be discussed in turn) close to the window 202 (e.g., where an output port of source 214 and an input port of optical detector 216 are adjacent the window 202). Transparent cap 204 may be a material that is substantially transparent to the wavelengths of excitation radiation 210 and fluorescence radiation 212 (e.g., materials that are transparent in the range of 250 to 700 nanometers, such as plexiglass or optical glass). Still other embodiments don't include cap 204.

Excitation radiation 210 may be generated by a source 214 that delivers excitation radiation 210 into first optical fiber 206 (or directly into window 202 in some embodiments where there is no optical fiber 206). In some embodiments, source 214 is a UV source that generates excitation radiation 210 having a peak wavelength between about 340 nm and 360 nm. Other optical sources, such as visible light or infrared (IR) sources, may be used as well depending on the fluorescent properties of the material of interest on workpiece 108. For many polymer materials, fluorescence is exhibited when absorbing UV light. An optical detector 216 may be used to receive fluorescence radiation 212 via second optical fiber 208 (or directly from window 202 in some embodiments where there is no optical fiber 208) and transduce the optical signal into an electrical signal that represents a magnitude of fluorescence radiation 212.

As can be further seen in this example embodiment, the electrical signal from optical detector 216 is received by a controller 218. According to some such embodiments, controller 218 controls the operations of tool 200, and the received electrical signal from optical detector 216 is used by controller 218 to change one or more operating conditions of substrate polishing tool 200. Since the magnitude of fluorescence radiation 212 is roughly proportional to the thickness of the polymer material (at least for thicknesses below a certain amount) on workpiece 108, the magnitude of fluorescence radiation 212 may be used by controller 218 to determine (or estimate) a thickness of the polymer material and take appropriate actions based on the thickness of the polymer material. For example, controller 218 may cease the rotation of polishing pad 104 and/or carrier structure 106 in response to the magnitude of fluorescence radiation 212 being lower than a threshold value. In another example scenario, controller 218 may raise carrier structure (with workpiece 108 attached) away from polishing pad 104 in response to the magnitude of fluorescence radiation 212 being lower than a threshold value.

Controller 218 can control other aspects of the processing as well, as will be appreciated. In some such embodiments, controller 218 may change the revolutions per minute (RPM) speed of either or both polishing pad 104 and carrier structure 106 based on the magnitude of fluorescence radiation 212. The change in RPM speed may involve continuous monitoring of the magnitude of fluorescence radiation 212 and subsequent adjustment to the RPM speed. In some embodiments, the RPM speed may be continually adjusted until a set-point magnitude of fluorescence radiation 212 (corresponding to a particular thickness of the polymer material) is reached. For example, if the magnitude of fluorescence radiation 212 is high above the set point (corresponding to a too-thick polymer film) then the RPM speed may start high or be increased to polish the polymer material more quickly. As the magnitude of fluorescence radiation 212 decreases, the RPM speed may similarly decrease until the setpoint is reached and the polishing operation is ceased.

According to some embodiments, data that relates fluorescence magnitudes to thicknesses for one or more different polymer materials may be stored in a memory coupled to controller 218. Such correlation data can be established empirically (e.g., by trial and error) or theoretically (e.g., by computer simulation), or both. In some cases, the data can be updated or modified by users, based on empirical analysis. In any such cases, the data may be accessed by controller 218 to determine the thickness of the polymer material on workpiece 108 associated with the received magnitude of fluorescence radiation 212. In some embodiments, a set-point thickness for the polymer material on workpiece 108 is provided by a user via a user-interface, and controller 218 controls the operations of substrate polishing tool 200 to ensure that the set-point thickness is achieved.

Different polymer materials will exhibit different fluorescence properties, and thus should be considered to accurately determine thickness of such materials, based on the established correlation. FIG. 3 is a graph showing arbitrary fluorescence counts received for different thicknesses of the polymer-based dielectric ABF when using excitation light at around 350 nm. The fluorescence radiation was received at around 395 nm. As will be appreciated, the wavelength of the excitation radiation and fluorescence radiation can vary greatly depending on the material being polished (e.g., 250 to 700 nanometers), and the present disclosure is not intended to be limited to any particular range of wavelengths.

As can be seen, a linear dependence on thickness exhibits for thicknesses below around 20 micrometers. Above this thickness, the excitation energy is likely unable to penetrate deeper into the polymer material, thus the fluorescence radiation does not continue to increase for increasing thicknesses. For thicknesses of ABF below around 20 micrometers, the fluorescence dependence data illustrated in FIG. 3 may be saved in a memory and accessed by controller 218 when comparing magnitudes of actual received fluorescence radiation 212. Similar such fluorescence vs. thickness curves can be produced for any number of different polymer materials and that resulting data may be stored in memory. The stored data may be indexed by polymer type or by optical characteristics such as the excitation wavelength used or the fluorescence wavelength.

Enhanced CMP Control for Bridge Interposer

One area that can benefit from accurately controlling the final polished thickness of polymer materials is the field of semiconductor packaging. Many semiconductor package schemes use polymer dielectrics when designing interconnect structures to connect semiconductor die(s) to a circuit board. One particular example is a bridge interconnect structure that uses a bridge die with other surrounding interconnect structures to provide electrical connections to more than one die on the same substrate. Polymer-based dielectrics, such as ABF, are used to encapsulate the bridge die and surrounding interconnect structures. If the thickness of the polymer dielectric is not well controlled, the bridge interconnect structure may fail to provide proper electrical connections to one or more of the semiconductor dies.

FIGS. 4A-4C illustrate cross sections of an example bridge interconnect structure during a critical CMP process of its upper-most polymer layer. It should be understood that the illustrated cross-sections do not show all layers of the bridge interconnect structure and that other interconnect layers may be present beneath the layers shown.

FIG. 4A illustrates a bridge interconnect structure having a polymer material 402 laminated or otherwise deposited over a plurality of interconnect structures 404 and a bridge die 406. Plurality of interconnect structures 404 represent one or more conductive traces and conductive vias fabricated on various metal layers, as would be understood to persons skilled in the relevant art. Bridge die 406 provides its own plurality of conductive interconnect structures.

As observed in FIG. 4A, the lamination or other deposition process for polymer material 402 leaves an uneven top surface. This top surface of polymer material 402 is planarized using a CMP process to provide a smooth, level surface for die coupling. FIG. 4B illustrates the bridge interconnect structure following a successful CMP process. Note that a final thickness t₁ of polymer material 402 is achieved. The CMP process may be controlled using the fluorescence detection techniques described herein to provide the desired final thickness t₁. Achieving the final thickness t₁ also provides a thickness t₂ of polymer material 402 above the top surface of bridge die 406. According to some embodiments, thickness t₂ should be thick enough to provide sufficient electrical isolation between conductive components on the top surface of polymer material 402 and underlying conductive structures. However, if it is too thick, then it would become difficult to fabricate vias to contact the different conductive portions of bridge die 406.

FIG. 4C illustrates the final bridge interconnect structure after formation of top-level interconnects 408 and top-level bridge interconnects 410. Also illustrated are two semiconductor dies coupled to the various top-level interconnects, which includes top-level bridge interconnects 410. In some examples, more than two die are coupled to a single bridge interconnect structure.

FIGS. 5A-5C illustrate cross sections of another example bridge interconnect structure during a critical CMP process of its upper-most polymer layer. Like the previous example, a polymer material 502 laminated or otherwise deposited over a plurality of interconnect structures 504 and a bridge die 506. However, in this example, top-level interconnects 508 and top-level bridge interconnects 510 are formed before the final lamination of further polymer material 502. In this design, the final thickness of polymer material 502 after CMP is even more critical. If polymer material 502 is too thick, the top surfaces of top-level interconnects 508 and top-level bridge interconnects 510 will not be exposed. If polymer material 502 is too thin, portions of top-level interconnects 508 and top-level bridge interconnects 510 will also be polished away, which can damage the structure.

FIG. 5B illustrates the bridge interconnect structure following a successful CMP process. The CMP process may be controlled using the fluorescence detection techniques described herein to provide the desired final thickness that exposes the top surfaces of top-level interconnects 508 and top-level bridge interconnects 510 without polishing away any substantial portions of the conductive vias.

FIG. 5C illustrates the final bridge interconnect structure after formation of top-level conductive pads 512 and top-level bridge pads 514 that contact the lower top-level interconnects 508 and top-level bridge interconnects 510, respectively. Also illustrated are two semiconductor dies coupled to the various top-level pads, which includes top-level bridge pads 514. In some examples, more than two die are coupled to a single bridge interconnect structure.

FIG. 6 illustrates substrate polishing tool 200 with many of the same labeled components from FIG. 2. In this example, the workpiece being polished is a panel 600 that includes a plurality of bridge interconnect structures. As noted before, only the top-most levels of the structures are illustrated for clarity, but other layers may be present as part of the bridge interconnect structures. Polymer material 602 may be polished across the entire panel 600 using polishing pad 104. Fluorescence radiation 210 may be collected from polymer material 602 during the polishing process to control the operation of substrate polishing tool 200, according to an embodiment.

Methodology

FIG. 7 is a flow chart of a method 700 for polishing a polymer material using fluorescence-based endpoint detection, according to an embodiment. The operations of method 700 may be performed to achieve a desired final thickness of the polymer material. Any other standard operations may be performed before, between, or after any illustrated operations of method 700 and have been omitted merely to focus on the operations most related to the polishing and fluorescence detection operations. The correlation of the various operations of method 700 to the specific components illustrated in FIG. 2 is not intended to imply any structural and/or use limitations.

Method 700 begins with operation 702 where the polymer material is coupled to a carrier structure of a substrate polishing tool. The polymer material may be laminated or otherwise deposited film on a workpiece and the workpiece is coupled to the carrier structure. The workpiece may be a wafer, die, panel, or any other type of substrate. The polymer may have a rough or uneven top surface that is to be planarized using the substrate polishing tool. The workpiece (with the polymer material) may be coupled to the carrier structure using an adhesive, electrostatic force, vacuum, or mechanical clamping, to name a few examples.

Method 700 continues with operation 704 where one or both of the carrier structure and a polishing pad are rotated to polish the polymer material. In some embodiments, the carrier structure is moved towards the polishing pad and applies pressure so that the polymer material is pushed against the polishing pad during the polishing process.

Method 700 continues with operation 706 where excitation light is generated and directed towards the polymer material. The excitation light may be UV light generated from a UV source. The excitation light can be directed towards the polymer material using one or more optical fibers. Depending on the type of polymer material, the peak wavelength of the excitation light can change to maximize the fluorescence radiation from the polymer material. For example, ABF exhibits fluorescence around 395 nm when absorbing excitation light around 350 nm. Other polymers may exhibit fluorescence in different portions of the electromagnetic spectrum. In some embodiments, the excitation light is directed via an optical fiber through an opening through the polishing pad to impinge upon the polymer material during the polishing process.

Method 700 continues with operation 708 where fluorescence radiation is received from the polymer material. The fluorescence radiation may be received via another optical fiber, or from the same optical fiber used to direct the excitation light towards the polymer material. The magnitude of the fluorescence radiation may be used to determine (or at least estimate) a thickness of the polymer material, at least within a linear operating portion of the response curve (as seen, for example, by the response curve of FIG. 6 for thicknesses below around 20 micrometers for ABF). Thus, the received fluorescence radiation allows the substrate polishing tool to have a real-time observation of the polymer thickness as the polymer is being polished.

Method 700 continues with operation 710 where one or more operating conditions of the substrate polishing tool is adjusted based on the received fluorescence radiation. Since the magnitude of the fluorescence radiation is roughly proportional to the thickness of the polymer material (at least for thicknesses below a certain amount), the magnitude of fluorescence radiation may be used by a controller to take appropriate actions based on the thickness of the polymer material. For example, the rotation of one or both of the polishing pad and carrier structure may be stopped in response to the magnitude of the fluorescence radiation being lower than a threshold value. In another example, the carrier structure (with the workpiece attached) can be moved away from the polishing pad in response to the magnitude of the fluorescence radiation being lower than a threshold value. These adjustments may be used to put a quick stop to the polishing process once a desired thickness of the polymer material has been achieved. In some other embodiments, the RPM of one or both the carrier structure and the polishing pad is lowered or raised depending on the magnitude of the fluorescence radiation.

Example Computing System for Process Control

FIG. 8 illustrates an example computing system 800 that may be coupled to one or more substrate polishing tools and may control operations of the one or more substrate polishing tools, in accordance with some embodiments of the present disclosure. In some embodiments, computing system 800 may host, or otherwise be incorporated into a personal computer, workstation, server system, laptop computer, ultra-laptop computer, tablet, touchpad, portable computer, handheld computer, palmtop computer, personal digital assistant (PDA), cellular telephone, combination cellular telephone and PDA, smart device (for example, smartphone or smart tablet), mobile internet device (MID), messaging device, data communication device, imaging device, wearable device, embedded system, and so forth. Any combination of different devices may be used in certain embodiments.

In some embodiments, computing system 800 may comprise any combination of a processor 802, a memory 804, a network interface 806, an input/output (I/O) system 808, a user interface 810, a storage system 812, and a CMP control module 818. As can be further seen, a bus and/or interconnect is also provided to allow for communication between the various components listed above and/or other components not shown. Computing system 800 can be coupled to a network 816 through network interface 806 to allow for communications with other computing devices, platforms, or resources. Other componentry and functionality not reflected in the block diagram of FIG. 8 will be apparent in light of this disclosure, and it will be appreciated that other embodiments are not limited to any particular hardware configuration.

Processor 802 can be any suitable processor and may include one or more coprocessors or controllers to assist in control and processing operations associated with computing system 800. In some embodiments, processor 802 may be implemented as any number of processor cores. The processor (or processor cores) may be any type of processor, such as, for example, a micro-processor, an embedded processor, a digital signal processor (DSP), a graphics processor (GPU), a network processor, a field programmable gate array or other device configured to execute code. The processors may be multithreaded cores in that they may include more than one hardware thread context (or “logical processor”) per core.

According to some embodiments of the present disclosure, CMP control module 818 can be any suitable processor and may include one or more coprocessors or controllers designed to control the operations of one or more substrate polishing tools. CMP control module 818 may receive magnitudes of fluorescence measurements taken from polymer materials being polished by the one or more substrate polishing tools, and adjust the operation of the one or more substrate polishing tools accordingly, according to some of the embodiments of the present disclosure. In some embodiments, the operations performed by CMP control module 818 are shared by, or entirely performed by, processor 802.

Memory 804 can be implemented using any suitable type of digital storage including, for example, flash memory and/or random access memory (RAM). In some embodiments, memory 804 may include various layers of memory hierarchy and/or memory caches as are known to those of skill in the art. Memory 804 may be implemented as a volatile memory device such as, but not limited to, a RAM, dynamic RAM (DRAM), or static RAM (SRAM) device. Storage system 812 may be implemented as a non-volatile storage device such as, but not limited to, one or more of a hard disk drive (HDD), a solid-state drive (SSD), a universal serial bus (USB) drive, an optical disk drive, tape drive, an internal storage device, an attached storage device, flash memory, battery backed-up synchronous DRAM (SDRAM), and/or a network accessible storage device. In some embodiments, storage system 812 may comprise technology to increase the storage performance enhanced protection for valuable digital media when multiple hard drives are included. According to some embodiments of the present disclosure, either or both memory 804 and storage system 812 includes data that associates fluorescence magnitude with thickness for a one or more different polymer materials.

Processor 802 may be configured to execute an Operating System (OS) 814 which may comprise any suitable operating system, such as Google Android (Google Inc., Mountain View, Calif.), Microsoft Windows (Microsoft Corp., Redmond, Wash.), Apple OS X (Apple Inc., Cupertino, Calif.), Linux, or a real-time operating system (RTOS).

Network interface 806 can be any appropriate network chip or chipset which allows for wired and/or wireless connection between other components of computing system 800 and/or network 816, thereby enabling computing system 800 to communicate with other local and/or remote computing systems, servers, cloud-based servers, and/or other resources. Wired communication may conform to existing (or yet to be developed) standards, such as, for example, Ethernet. Wireless communication may conform to existing (or yet to be developed) standards, such as, for example, cellular communications including LTE (Long Term Evolution), Wireless Fidelity (Wi-Fi), Bluetooth, and/or Near Field Communication (NFC). Exemplary wireless networks include, but are not limited to, wireless local area networks, wireless personal area networks, wireless metropolitan area networks, cellular networks, and satellite networks.

I/O system 808 may be configured to interface between various I/O devices and other components of computing system 800. I/O devices may include, but not be limited to, a user interface 810. User interface 810 may include devices (not shown) such as a display element, touchpad, keyboard, mouse, and speaker, etc. I/O system 808 may include a graphics subsystem configured to perform processing of images for rendering on a display element. Graphics subsystem may be a graphics processing unit or a visual processing unit (VPU), for example. An analog or digital interface may be used to communicatively couple graphics subsystem and the display element. For example, the interface may be any of a high definition multimedia interface (HDMI), DisplayPort, wireless HDMI, and/or any other suitable interface using wireless high definition compliant techniques. In some embodiments, the graphics subsystem could be integrated into processor 802 or any chipset of computing system 800.

It will be appreciated that in some embodiments, the various components of the computing system 800 may be combined or integrated in a system-on-a-chip (SoC) architecture. In some embodiments, the components may be hardware components, firmware components, software components or any suitable combination of hardware, firmware or software.

In various embodiments, computing system 800 may be implemented as a wireless system, a wired system, or a combination of both. When implemented as a wireless system, computing system 800 may include components and interfaces suitable for communicating over a wireless shared media, such as one or more antennae, transmitters, receivers, transceivers, amplifiers, filters, control logic, and so forth. An example of wireless shared media may include portions of a wireless spectrum, such as the radio frequency spectrum and so forth. When implemented as a wired system, computing system 800 may include components and interfaces suitable for communicating over wired communications media, such as input/output adapters, physical connectors to connect the input/output adaptor with a corresponding wired communications medium, a network interface card (NIC), disc controller, video controller, audio controller, and so forth. Examples of wired communications media may include a wire, cable metal leads, printed circuit board (PCB), backplane, switch fabric, semiconductor material, twisted pair wire, coaxial cable, fiber optics, and so forth.

Unless specifically stated otherwise, it may be appreciated that terms such as “processing,” “computing,” “calculating,” “determining,” or the like refer to the action and/or process of a computer or computing system, or similar electronic computing device, that manipulates and/or transforms data represented as physical quantities (for example, electronic) within the registers and/or memory units of the computer system into other data similarly represented as physical quantities within the registers, memory units, or other such information storage transmission or displays of the computer system. The embodiments are not limited in this context.

Further Example Embodiments

The following examples pertain to further embodiments, from which numerous permutations and configurations will be apparent.

Example 1 is a polishing tool that includes a carrier structure supporting a workpiece, a polishing pad, a source, a detector, and a controller. The polishing pad rotates and polishes at least a portion of the workpiece. The source generates excitation radiation directed towards the workpiece while the detector receives fluorescence radiation from the workpiece. The fluorescence radiation is generated by absorption of the excitation radiation. The controller is designed to change at least one operating condition of the polishing tool based on a magnitude of the received fluorescence radiation.

Example 2 includes the subject matter of Example 1, wherein the source comprises an ultraviolet (UV) source.

Example 3 includes the subject matter of Example 1 or 2, further comprising a first optical fiber configured to direct the generated excitation radiation towards the workpiece, and a second optical fiber configured to collect fluorescence radiation from the workpiece and to direct the fluorescence radiation towards the detector.

Example 4 includes the subject matter of any one of Examples 1-3, wherein the controller is configured to halt rotation of the polishing pad in response to the magnitude of the received fluorescence radiation falling below a threshold value.

Example 5 includes the subject matter of any one of Examples 1-3, wherein the controller is configured to increase or decrease a rotation speed of the polishing pad based on the magnitude of the received fluorescence radiation.

Example 6 includes the subject matter of any one of Examples 1-5, further comprising a memory configured to store data that associates given thicknesses of a polymer material with corresponding fluorescence magnitudes.

Example 7 includes the subject matter of Example 6, wherein the controller is configured to compare the magnitude of the received fluorescence radiation to the stored data having corresponding fluorescence magnitudes to determine a thickness of the polymer material present on the workpiece.

Example 8 is a method of polishing a polymer material. The method includes bringing the polymer material, via a carrier structure, into contact with a polishing pad; rotating the polishing pad to polish the polymer material; directing excitation radiation towards the polymer material; receiving fluorescence radiation from the polymer material, the fluorescence radiation generated from absorption of the excitation radiation; and adjusting an operating condition of at least one of the polishing pad and the carrier structure based on a magnitude of the received fluorescence radiation.

Example 9 includes the subject matter of Example 8, wherein the polymer material comprises a polymer film that encapsulates at least a portion of a semiconductor die.

Example 10 includes the subject matter of Example 8 or 9, wherein directing excitation radiation comprises directing UV radiation towards the polymer material.

Example 11 includes the subject matter of any one of Examples 8-10, wherein directing excitation radiation comprises directing excitation radiation via a first optical fiber towards the polymer material, and wherein receiving fluorescence radiation comprises receiving fluorescence radiation via a second optical fiber from the polymer material.

Example 12 includes the subject matter of any one of Examples 8-11, wherein the adjusting comprises halting rotation of the polishing pad.

Example 13 includes the subject matter of any one of Examples 8-12, further comprising: accessing stored data from a memory, the stored data including thicknesses of the polymer material with corresponding fluorescence magnitudes; and comparing the magnitude of the received fluorescence radiation to the corresponding fluorescence magnitudes in the stored data.

Example 14 is a chemical mechanical process apparatus that is designed to execute the method of any one of claims 8-13.

Example 15 is a computer program product including one or more non-transitory machine-readable mediums encoding instructions that when executed by one or more processors cause a process to be carried out for polishing a polymer material. The process includes actuating a carrier structure coupled to the polymer material, to bring the polymer material into contact with a polishing pad; rotating the polishing pad to polish the polymer material; receiving fluorescence data associated with fluorescence radiation from the polymer material; and adjusting an operating condition of at least one of the polishing pad and the carrier structure based on a magnitude of the fluorescence data.

Example 16 includes the subject matter of Example 15, wherein the adjusting comprises one or both of: halting rotation of the polishing pad; increasing a rotation speed of the polishing pad; and decreasing the rotation speed of the polishing pad.

Example 17 includes the subject matter of Example 15 or 16, wherein the adjusting comprises actuating the carrier structure to move the polymer material away from the polishing pad.

Example 18 includes the subject matter of any one of Examples 15-17, wherein the process further comprises: accessing stored data from a memory, the stored data having given thicknesses of the polymer material with corresponding fluorescence magnitudes; and comparing the magnitude of the received fluorescence data to the corresponding fluorescence magnitudes in the stored data.

Example 19 includes the subject matter of Example 18, wherein the process further comprises determining a thickness of the polymer material based on the comparing.

Example 20 is a chemical mechanical process apparatus that includes the computer program product of any one of claims 15-19.

The foregoing description of example embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto. 

What is claimed is:
 1. A polishing tool, comprising: a carrier structure configured to support a workpiece; a polishing pad configured to rotate and polish at least a portion of the workpiece; a source configured to generate excitation radiation directed towards the workpiece; a detector configured to receive fluorescence radiation from the workpiece, the fluorescence radiation generated by absorption of the excitation radiation; and a controller configured to, based on a magnitude of the received fluorescence radiation, change at least one operating condition of the polishing tool.
 2. The polishing tool of claim 1, wherein the source comprises an ultraviolet (UV) source.
 3. The polishing tool of claim 1, further comprising a first optical fiber configured to direct the generated excitation radiation towards the workpiece, and a second optical fiber configured to collect fluorescence radiation from the workpiece and to direct the fluorescence radiation towards the detector.
 4. The polishing tool of claim 1, wherein the controller is configured to halt rotation of the polishing pad in response to the magnitude of the received fluorescence radiation falling below a threshold value.
 5. The polishing tool of claim 1, wherein the controller is configured to increase or decrease a rotation speed of the polishing pad based on the magnitude of the received fluorescence radiation.
 6. The polishing tool of claim 1, further comprising a memory configured to store data that associates given thicknesses of a polymer material with corresponding fluorescence magnitudes.
 7. The polishing tool of claim 6, wherein the controller is configured to compare the magnitude of the received fluorescence radiation to the stored data having corresponding fluorescence magnitudes to determine a thickness of the polymer material present on the workpiece.
 8. A method of polishing a polymer material, the method comprising: bringing the polymer material, via a carrier structure, into contact with a polishing pad; rotating the polishing pad to polish the polymer material; directing excitation radiation towards the polymer material; receiving fluorescence radiation from the polymer material, the fluorescence radiation generated from absorption of the excitation radiation; and adjusting an operating condition of at least one of the polishing pad and the carrier structure based on a magnitude of the received fluorescence radiation.
 9. The method of claim 8, wherein the polymer material comprises a polymer film that encapsulates at least a portion of a semiconductor die.
 10. The method of claim 8, wherein directing excitation radiation comprises directing UV radiation towards the polymer material.
 11. The method of claim 8, wherein directing excitation radiation comprises directing excitation radiation via a first optical fiber towards the polymer material, and wherein receiving fluorescence radiation comprises receiving fluorescence radiation via a second optical fiber from the polymer material.
 12. The method of claim 8, wherein the adjusting comprises halting rotation of the polishing pad.
 13. The method of claim 8, further comprising: accessing stored data from a memory, the stored data including thicknesses of the polymer material with corresponding fluorescence magnitudes; and comparing the magnitude of the received fluorescence radiation to the corresponding fluorescence magnitudes in the stored data.
 14. A chemical mechanical process apparatus configured to execute the method of claim
 8. 15. A computer program product including one or more non-transitory machine-readable mediums encoding instructions that when executed by one or more processors cause a process to be carried out for polishing a polymer material, the process comprising: actuating a carrier structure coupled to the polymer material, to bring the polymer material into contact with a polishing pad; rotating the polishing pad to polish the polymer material; receiving fluorescence data associated with fluorescence radiation from the polymer material; and adjusting an operating condition of at least one of the polishing pad and the carrier structure based on a magnitude of the fluorescence data.
 16. The computer program product of claim 15, wherein the adjusting comprises one or both of: halting rotation of the polishing pad; increasing a rotation speed of the polishing pad; and decreasing the rotation speed of the polishing pad.
 17. The computer program product of claim 15, wherein the adjusting comprises actuating the carrier structure to move the polymer material away from the polishing pad.
 18. The computer program product of claim 15, wherein the process further comprises: accessing stored data from a memory, the stored data having given thicknesses of the polymer material with corresponding fluorescence magnitudes; and comparing the magnitude of the received fluorescence data to the corresponding fluorescence magnitudes in the stored data.
 19. The computer program product of claim 18, wherein the process further comprises determining a thickness of the polymer material based on the comparing.
 20. A chemical mechanical process apparatus including the computer program product of claim
 15. 